Recent measurements reveal that the Universe is at least 150 billion light-years in diameter. For comparison, its age is estimated to be about 13.7 billion years. Doesn’t make sense does it?
Since some of you may be wondering what kind of disparity we’re talking about, let me elaborate. You see, to arrive at that age, scientists had to measure light (or electromagnetic radiation) coming from the outermost borders of the Universe. This radiation, specifically known as the cosmic microwave background radiation is a throwback to the youngest years of the Universe. So if it had to take 13.7 billion years for light coming from the outermost regions to reach us, then we should be expecting a diameter within that order of magnitude. Simply put, around twice that value or 27.4 billion light-years. But lo and behold, we’re seeing a number much much larger than that.
This value, however, only makes sense if our Universe’s size were constant. Studies have shown that that isn’t the case. In fact, separate observations have shown that the Universe is actually expanding. To top it all, it is confirmed that it does so at an accelerated rate.
Lets make a very simplified analogy, just to give us a rough idea regarding the source of discrepancy. Imagine yourself having a friend standing on a planet at the outermost galaxy. Lets also assume you both have superhuman strength and are able to play catch with indestructible balls (whose constant speed you both know) that takes a straight path, and that no obstruction exists along the said path.
If he throws a ball, you’d be able to determine either the time of flight or the distance traveled if you knew the other physical quantity. Thus, if the time of flight is 13.7 billion years and the ball was traveling at the speed of light, neglecting relativistic effects, the distance should be 13.7 billion light-years.
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